package com.hit.basmath.learn.others;

/**
 * 661. Image Smoother
 * <p>
 * Given a 2D integer matrix M representing the gray scale of an image, you need to design a smoother to make the gray scale of each cell becomes the average gray scale (rounding down) of all the 8 surrounding cells and itself. If a cell has less than 8 surrounding cells, then use as many as you can.
 * <p>
 * Example 1:
 * <p>
 * Input:
 * [[1,1,1],
 * [1,0,1],
 * [1,1,1]]
 * <p>
 * Output:
 * [[0, 0, 0],
 * [0, 0, 0],
 * [0, 0, 0]]
 * <p>
 * Explanation:
 * <p>
 * For the point (0,0), (0,2), (2,0), (2,2): floor(3/4) = floor(0.75) = 0
 * For the point (0,1), (1,0), (1,2), (2,1): floor(5/6) = floor(0.83333333) = 0
 * For the point (1,1): floor(8/9) = floor(0.88888889) = 0
 * <p>
 * Note:
 * <p>
 * The value in the given matrix is in the range of [0, 255].
 * The length and width of the given matrix are in the range of [1, 150].
 */
public class _661 {
    public int[][] imageSmoother(int[][] M) {
        if (M == null) return null;
        int rows = M.length;
        if (rows == 0) return new int[0][];
        int cols = M[0].length;

        int result[][] = new int[rows][cols];

        for (int row = 0; row < rows; row++) {
            for (int col = 0; col < cols; col++) {
                int count = 0;
                int sum = 0;
                for (int incR : new int[]{-1, 0, 1}) {
                    for (int incC : new int[]{-1, 0, 1}) {
                        if (isValid(row + incR, col + incC, rows, cols)) {
                            count++;
                            sum += M[row + incR][col + incC];
                        }
                    }
                }
                result[row][col] = sum / count;
            }
        }

        return result;

    }

    private boolean isValid(int x, int y, int rows, int cols) {
        return x >= 0 && x < rows && y >= 0 && y < cols;
    }
}
